ox: Add Icelandic quotes

* lisp/ox.el (org-export-smart-quotes-alist): Add Icelandic quotes.

Suggested-by: Jón Gunnar Þorsteinsson <jongth@hi.is>

lisp/ox.el

@@ -5251,6 +5251,16 @@ Return a list of src-block elements with a caption."
      (secondary-closing :utf-8 " »" :html " »" :latex "\\fg{}"
 			:texinfo "@tie{}@guillemetright{}")
      (apostrophe :utf-8 "’" :html "’"))
+    ("is"
+     (primary-opening
+      :utf-8 "„" :html "„" :latex "\"`" :texinfo "@quotedblbase{}")
+     (primary-closing
+      :utf-8 "“" :html "“" :latex "\"'" :texinfo "@quotedblleft{}")
+     (secondary-opening
+      :utf-8 "‚" :html "‚" :latex "\\glq{}" :texinfo "@quotesinglbase{}")
+     (secondary-closing
+      :utf-8 "‘" :html "‘" :latex "\\grq{}" :texinfo "@quoteleft{}")
+     (apostrophe :utf-8 "’" :html "’"))
     ("no"
      ;; https://nn.wikipedia.org/wiki/Sitatteikn
      (primary-opening